Tumorigenesis in humans is a complex process involving activation of oncogenes and inactivation of tumor suppressor genes (Bishop, 1991, Cell 64:235-248). Tumor suppressor genes in humans have been identified through studies of genetic changes occurring in cancer cells (Ponder, 1990, Trends Genet. 6:213-218; Weinberg, 1991, Science 254:1138-1146). In Drosophila, tumor suppressor genes have been previously identified by recessive overproliferation mutations that cause late larval and pupal lethality (Gateff, 1978, Science 200:1448-1459; Gateff and Mechler, 1989, CRC Crit. Rev. Oncogen 1:221-245; Bryant, 1993, Trends Cell Biol. 3:31-35; Torok et al., 1993, Genetics 135:71-80). Mutations of interest were identified when dissection of dead larvae and pupae revealed certain overproliferated tissues. Several genes identified in homozygous mutants have been cloned including 1(1)discs large-1(dlg; Woods and Bryant, 1991, Cell 66:451-464; Woods and Bryant, 1993, Mechanisms of Development 44:85-89), fat (Mahoney et al., 1991, Cell 67:853-868), l(2)giant larvae (lgl. Lutzelschwab et al., 1987, EMBO J. 6:1791-1797; Jacob et al., 1987, Cell 50:215-225), expanded (ex; Boedigheimer and Laughon, 1993, Development 118:1291-1301; Boedigheimer et al., 1993, Mechanisms of Development 44:83-84), hyperplastic discs (hyd; Mansfield et al., 1994, Developmental Biology 165:507-526) and the gene encoding the S6 ribosomal protein (Watson et al., 1992, Proc. Natl. Acad. Sci. USA 89:11302-11306; Stewart and Denell, 1993, Mol. Cell. Biol. 13:2524-2535).
Although examining homozygous mutant animals has allowed the successful identification of overproliferation mutations that cause late larval and pupal lethality, mutations that cause lethality at early developmental stages are unlikely to be recovered by this approach. The present invention solves this problem by providing a method for identifying tumor suppressor genes that does not exclude genes that when mutated cause lethality in early developmental stages, and provides genes thus identified with a fundamental role in regulation of cell proliferation.
Citation of references hereinabove shall not be construed as an admission that such references are prior art to the present invention.